Interesting comment by the Raps announcer. 18 seconds left, tie game, Heat ball. He says foul'em, and take your chances they miss a free throw. If not, you still have plenty of time to run a play and get a 3 or play for a quick 2. His reasoning being that the Heat are clearly the superior team and you don't want to go to overtime with them.
I like the idea. Raptors probably win 1 or 2 in 10 vs the Heat in OT. Take the chance to give yourself the final shot to win the game. If they miss a free throw, you're probably going to win the game about 40% of the time. If they make both, probably about 30% of the time. Better odds than the Raptor beating the Heat in OT.
I doubt any coach would have the balls to try it though.
I think its an interesting question but your percentages feel way off. You are making an assumption that if the Heat miss 1 or the Raptors make a 3 that the Heat dont get the ball back, so the quality of shot will be much lower than if they run a normal offense and leave like 5 seconds left. I think 40% is way too high if you want a buzzer beater shot (which you HAVE to do in this case because you dont want Miami having the ball last since you are fouling with 18 seconds).
The 30%number on if Miami hits both is absurd. League average for 3's is around 30-35% i believe, but in the waning seconds of a 1 possession game i would bet it falls well below 30% since the defense is prepared for a 3 pointer. Too many variables to do this, you just have to hope the Heat miss the last shot. One thing you didnt mention that could help your cause is the Heats chances of winning in regulation and if they miss than add in the Raptors OT chances (which you estimated at 20%) Like Baseball has win probabilities, I am sure there is a basketball win Probabilities somewhere analyzing what the proper play really is.